CardioNet Inc. is facing a probe by the Department of Justice over allegations that the company used inappropriate diagnosis codes when submitting claims for payment to Medicare for its real-time outpatient cardiac monitoring services. CardioNet said that it received a Civil Investigative Demand issued by DOJ for documents for the period January 1 2007 through the date of the CID. CardioNet provides ambulatory, continuous and real time outpatient management solutions for monitoring relevant and time clinical information about a person’s health.